Part of what makes it a steep rather than a mash is also the types of grains you are using. If you were mashing you need some kind of base malt to aid in starch conversion and extract sugars; since you are only using specialty grains you are only steeping regardless of how long you leave the grains in the water.
Once you make a mash tun you will need to replace some of your extract additions with 2-row or some other base malt in the mash.